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Thread Subject: Empty array gets added to. (Or not)

Subject: Empty array gets added to. (Or not)

From: Andr?

Date: 16 Oct, 2009 09:56:03

Message: 1 of 2

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Hi.

I discovered that

a=[];
b=4;
a=a+b;

will not yield an error message as would

a = a+4;

(without first assigning a). Yet it also does not give a=4... I knew that Nan+4 =NaN, but why is []+4=[] ? Is there more 'black hole beahviour' i should know about?

Thank you.

Andr

Subject: Empty array gets added to. (Or not)

From: Loren Shure

Date: 16 Oct, 2009 12:05:29

Message: 2 of 2

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In article <hb9fvj$i37$1@fred.mathworks.com>, bukwyrm@googlemail.com
says...
> Hi.
>
> I discovered that
>
> a=[];
> b=4;
> a=a+b;
>
> will not yield an error message as would
>
> a = a+4;
>
> (without first assigning a). Yet it also does not give a=4... I knew that Nan+4 =NaN, but why is []+4=[] ? Is there more 'black hole beahviour' i should know about?
>
> Thank you.
>
> Andr
>

b is a scalar and MATLAB addition adheres to the scalar expansion rule,
i.e., anything + scalar is size of anything. Hence you get empty as the
output for a in your example.

--
Loren
http://blogs.mathworks.com/loren

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Tag Activity for This Thread
Tag	Applied By	Date/Time
array	Andr?	16 Oct, 2009 05:59:04
empty	Andr?	16 Oct, 2009 05:59:04
nan	Andr?	16 Oct, 2009 05:59:04

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